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From: Vitaly Kuznetsov <vkuznets@redhat.com>
References: <20180312151233.16565-1-vkuznets@redhat.com>
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	<7d1afa27-9653-75dc-ebfe-8633b93f1ce6@redhat.com>
Date: Fri, 16 Mar 2018 16:05:40 +0100
In-Reply-To: <7d1afa27-9653-75dc-ebfe-8633b93f1ce6@redhat.com> (Paolo
	Bonzini's message of "Fri, 16 Mar 2018 15:49:30 +0100")
Message-ID: <87efkk9i2j.fsf@vitty.brq.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] i386/kvm: lower requirements for
 Hyper-V frequency MSRs exposure
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Roman Kagan <rkagan@virtuozzo.com>, qemu-devel@nongnu.org

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 12/03/2018 16:12, Vitaly Kuznetsov wrote:
>>  
>> -        if (has_msr_hv_frequencies && tsc_is_stable_and_known(env)) {
>> +        if (has_msr_hv_frequencies && env->tsc_khz) {
>
> Should this be
>
> ((env->tsc_khz && has_msr_hv_reenlightenment) ||
>  tsc_is_stable_and_known(env))
>
> so that you don't regress on older kernels?
>

I don't actually see where the regression might come from: frequency
MSRs are supported regardless or reenlightenment/invtsc and there's
nothing wrong with exposing them but I may be missing something..

-- 
  Vitaly